Cathode ray tubes (CRTs) are typically heavy and bulky. To resolve or obviate these physical disadvantages of the CRTs, flat display devices have been developed. Examples of the flat display devices are a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electro-luminescence (EL) display device.
The EL display is a self-luminous device that emits light by using a fluorescent material through a recombination of electron and hole. The EL display device falls into two classifications, inorganic and organic, according to corresponding materials and structures. Unlike the LCD, the EL display device does not utilize a separate light source so as to be lightweight and slim. Moreover, the EL display device has a response time comparable to that of the CRT.
FIG. 1 is a sectional view illustrating an organic light-emitting cell of a related art EL display panel.
Referring to FIG. 1, the organic light-emitting cell includes an electron injection layer 4, an electron transport layer 6, an emission layer 8, a hole transport layer 10, and a hole injection layer 12, which are sequentially stacked between a cathode 2 and an anode 14.
When a predetermined voltage V is applied between the anode 14 of a transparent electrode and the cathode 2 of a metal electrode, electrons from the cathode 2 move toward the emission layer 8 through the electron injection layer 4 and the electron transport layer 6. Also, holes from the anode 14 move toward the emission layer 8 through the hole injection layer 12 and the hole transport layer 10. The electrons from the electron transport layer 6 and the holes from the hole transport layer 10 are recombined in the emission layer 8, thereby generating light. Then, the generated light is emitted to the outside through the anode 14 of the transparent electrode and then an image is displayed.
FIG. 2 is a schematic view of a prior art electro-luminescence display device.
Referring to FIG. 2, a related art EL display device includes an EL display panel 16 with subpixels 22, a scan driver 18 for driving scan lines SL1 to SLn, a data driver 20 for driving data lines DL1 to DLm, and a timing controller 28 for controlling the driving timing of the data diver 20 and the scan driver 18. The subpixels 22 are arranged at each pixel region defined by intersections of the scan lines SL1 to SLn and the data lines DL1 to DLm.
One pixel includes R, G and B subpixels 22 arranged in a horizontal direction. Each of the subpixels 22 includes a power supply (VDD) (not shown), an emitting-light cell (OLED) (not shown) connected between the power source (VDD) and a ground source (GND) (not shown), and an emitting-light cell driving circuit (not shown) for driving the emitting-light cell according to a driving signal supplied from the data line DL and the scan line SL.
The timing controller 28 generates a scan control signal for controlling the scan driver 18 and a data control signal for controlling the data driver 20 in response to synchronization signals supplied from an external system (e.g. a graphic card). Also, the timing controller 28 supplies data signal from the external system to the dada driver 20.
The scan driver 18 generates a scan pulse (SP) in response to the scan control signal outputted from the timing controller 28, and transfers the scan pulse (SP) to the scan lines SL1 to SLn, thereby driving the scan lines SL1 to SLn in sequence.
The data driver 20 supplies a current signal to data lines DL1 to DLm according to the data control signal outputted from the timing controller 28. The current signal has a current level or pulse width responsive to the data signal at each horizontal period (1H). As such, the data driver 20 has DLm number of output channels, which are matched one-to-one with the data lines DL1 to DLm.
The EL display device supplies each of the subpixels 22 with the current signal having a current level or pulse width proportional to input data. Then, each of the subpixels 22 emits light in proportion to an amount of current supplied from each of the data lines DL.
In the described EL display device, the scan driver 18 is disposed in one side of the EL display panel 16 in a vertical direction and is integrated into the panel 16.
Referring to FIG. 2, in the described EL display panel 16 in which R, G and B subpixels 22 are arranged in this order in a horizontal direction, the scan driver 18 includes n number of circuit parts 19 each corresponding to a height A of each of the subpixels 22. Each of the circuit parts 19 has a predetermined width B. That is, the number of the circuit terminals 19 corresponds to that of the scan lines SL1 to SLn arranged in the EL display panel 16. As such, each circuit part 19 has a layout area given by multiplying the height A of each subpixel 22 by the width B of each circuit part 19.
The circuit parts 19 provide a turn-on voltage to a plurality of subpixels 22 connected to the scan lines SL1 to SLn.
The scan driver 18 of the related art EL display device needs a layout area corresponding to “height A of each subpixel×width B of each circuit terminal×number (n) of the scan lines”.
When the scan driver 18 is disposed in only one side of the panel 16, the layout area as wide as the scan driver 18 is disposed in only one side of the EL display panel 16. Therefore, the display panel 16 is not placed in the middle of the EL display device. Moreover, an entire size of the EL display device increases as the layout area of the scan driver 18 increases.